Since the concept of molecular electronics was first proposed in 1974 by Aviram and Ratner (A. Aviram et al, Chemical Physics Letters, Vol. 29, pp. 277-283 (1974)), numerous studies have focused on probing single molecules in terms of using molecules directly as functional electric circuit components such as switches, diodes, or even transistors in replacement of conventional semiconductors, specifically, silicon. On another hand, the interaction of organic species with silicon surfaces remains a topic of considerable extent waiting to be explored, and the ability to tailor the surface electronic properties of silicon by organic or organo-metallic molecules poses a fascinating area hardly conceivable in the past. Cahen and coworkers (N. Zenou et al, ACS Sym. Ser., Vol. 695, pp. 57-66 (1998)) have pointed out that the electronic properties of silicon can be tuned by molecules with different electron-donating or electron-withdrawing groups on the surface. However, the molecules they discussed can only alter the silicon electronic properties once, not in a reversible or tunable fashion.
Thus, the reversible/tunable alteration of the electronic properties of silicon is needed.